OxyElite Pro, a popular line of fat-burning dietary supplements produced by USPlabs LLC, has been linked to the death of one Hawaiian resident and more than two dozen cases of non-viral hepatitis, according to the U.S. Food and Drug Administration (FDA).

Twenty-nine people in Hawaii have been diagnosed with acute hepatitis in the past 11 months. Eleven were hospitalized, two required liver transplants, and one died. Most of the patients reported using USPlabs’ OxyElite Pro, a dietary supplement available in powder or capsules. It costs nearly 60 dollars when purchased directly from the manufacturer. Health regulators, however, are exploring the possibility that a cheap knockoff may have caused the illnesses, Law360.com reported.

“Because USPlabs LLC has informed FDA that it believes counterfeit versions of OxyElite Pro are being marketed in the U.S. and have been on the U.S. market for some time, the FDA is also investigating whether counterfeit product is related to any of the cases of acute hepatitis,” regulators said.

The domestic distribution of OxyElite has been halted and will remain so for the duration of the investigation, according to Law360.com.